Optical connector and adapter

ABSTRACT

A system for connecting a fiber optic connector to a fiber optic adapter includes various alternative improvements, including improvements to the shutter, the alignment device, and the adapter in general.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.17/129,044, filed on Dec. 21, 2020, which Continuation of U.S. patentapplication Ser. No. 16/523,077, filed on Jul. 26, 2019, now U.S. Pat.No. 10,871,616, which is a Continuation of U.S. patent application Ser.No. 16/098,382, filed on Nov. 1, 2018, now U.S. Pat. No. 10,409,007,which is a National Stage Application of PCT/US2017/030450, filed on May1, 2017, which claims the benefit of U.S. Patent Application Ser. No.62/330,655, filed on May 2, 2016, and claims the benefit of U.S. PatentApplication Ser. No. 62/447,984, filed on Jan. 19, 2017, the disclosuresof which are incorporated herein by reference in their entireties.

BACKGROUND

Optical adapters are used to optically couple together optical fibers ofoptical connectors. An optical adapter typically includes an alignmentstructure that coaxially aligns the optical fibers of the connectorsdesired to be optically connected together. Optical connectors can besecured to the optical adapter by being received at ports of the opticaladapter.

In certain examples, the optical connectors include ferrule-less opticalconnectors. For example, an example ferrule-less optical connector 10known in the art is shown at FIG. 1 . The optical connector 10 includesa connector body 11 having a front mating end 12 (plug end) and a rearcable terminating end 13. An optical fiber extends forwardly through theconnector body 11 and has a ferrule-less end portion that is accessibleat the front mating end 12 of the connector body 11. A shutter 15protects the ferrule-less end portion of the optical fiber fromcontamination when shut and allows access to the ferrule-less endportion when open. The shutter 15 can move between closed and openpositions.

The connector 10 also includes a latch 16 that engages a catch of afiber optic adapter for holding the connector 10 in place once coupledwith the adapter. When the connectors 10 are inserted within coaxiallyaligned ports of the adapter, the shutters 15 of the connectors 10 areretracted, thereby exposing the ferrule-less ends of the optical fibers.Continued insertion causes the ferrule-less ends to enter the opticalfiber alignment device. In an example, the fiber alignment deviceincludes funnels or funnel-like structures leading to a fiber alignmentslot, and biasing members pressing the fibers into the slot. Otherexamples of ferrule-less optical connectors and corresponding opticaladapters can be found in U.S. patent application Ser. No. 14/377,189,filed Aug. 7, 2014, titled “Optical Fiber Connection System IncludingOptical Fiber Alignment Device,” and issued as U.S. Pat. No. 9,575,263.The optical fiber is anchored adjacent the rear cable terminating end 13against axial movement relative to the connector body 11. When twoconnectors 10 are coupled together, the end faces of the ferrule-lessend portions abut one another, thereby causing the optical fibers to beforced rearwardly into the connector bodies 11 and to buckle/bend withinfiber buckling regions of the connector bodies 11.

SUMMARY

One aspect of the present disclosure relates to a fiber optic connectorhaving effective fiber end protection and structure for inhibiting backreflection of optical signal. According to some aspects, the fiber opticconnector comprises a plug body defining a distal plug end and anopposite proximal end; an optical fiber defining a fiber axis, theoptical fiber extending along the fiber axis at least partially throughthe plug body, the optical fiber including a free end portion thatextends outwardly from the plug body distally beyond the plug end, thefree end portion of the optical fiber not being supported by a ferrule;a shutter pivotally connected to the plug body and pivotally movablerelative to the plug body between an open position and a closedposition, the shutter including an interior receptacle that receives thefree end portion of the optical fiber when the shutter is in the closedposition. The interior receptacle is defined at least in part by a lightdistribution structure including a plurality of facet surfaces angledrelative to one another, the light distribution structure beingintersected by the fiber axis when the shutter is in the closedposition. Index matching gel is positioned within the interiorreceptacle of the shutter, the index matching gel covering at least aportion of the light distribution structure such that the free endportion of the optical fiber is embedded within the index matching gelwhen the shutter is in the closed position.

According to some aspects, a fiber optic adapter comprises an adapterbody defining an adapter axis, the adapter body defining a firstconnector port aligned along the adapter axis, the adapter body alsodefining a second connector port aligned along the adapter axis, thefirst connector port having an open end that faces in a first axialdirection, and the second connector port having an open end that facesin a second axial direction. A fiber alignment groove extends axiallythrough at least a portion of the adapter body, the fiber alignmentgroove including a first portion corresponding to the first connectorport and a second portion corresponding to the second connector port,the fiber alignment groove having an open side that extends axiallyalong the fiber alignment groove. Three discrete fiber biasing membersoppose the fiber alignment groove for pressing optical fibers into thefiber alignment groove, with one biasing member positioned at a midpointbetween the other two.

The adapter may also comprise an alignment device with an offset fibercontact location. The fiber alignment groove is bisected by a referenceplane that includes the adapter axis. A first fiber biasing memberopposes the first portion of the fiber alignment groove, the first fiberbiasing member having a fiber contact location that is offset in a firstlateral direction from the reference plane by a lateral offset distanceof at least 0.05 mm. A second fiber biasing member opposes the secondportion of the fiber alignment groove, the second fiber biasing memberhaving a fiber contact location that is offset in the first lateraldirection from the reference plane by a lateral offset distance of atleast 0.05 mm.

In some aspects, the adapter is constructed to accommodate more fiberbuckling at one side of the adapter than the other. The adapter bodydefines an adapter axis, and a first connector port and second connectorport aligned along the adapter axis. The adapter body is bisected by afirst reference plane that is perpendicular relative to the adapteraxis. A fiber alignment structure is mounted within the adapter bodyincluding a fiber alignment groove that extends axially through at leasta portion of the adapter body along the adapter axis, the fiberalignment groove including a first portion corresponding to the firstconnector port and a second portion corresponding to the secondconnector port, the fiber alignment groove having an open side thatextends axially along the fiber alignment groove. The fiber alignmentstructure is bisected by a second reference plane that is perpendicularrelative to the adapter axis, the second reference plane being offsetfrom the first reference plane in a direction toward the secondconnector port. The fiber alignment structure includes a first fiberbiasing member that opposes the first portion of the fiber alignmentgroove and a second fiber biasing member that opposes the second portionof the fiber alignment groove.

In some aspects, the adapter includes an adapter body defining anadapter axis, a first connector port, and a second connector portaligned along the adapter axis, and an indication for directing atechnician to install a fiber optic connector in the first connectorport before installing a second fiber optic connector in the secondconnector port. In another aspect, the adapter includes a structure thatprevents a second fiber optic connector from being installed in thesecond connector port before installing a first fiber optic connector inthe first port. The adapter can include a first connector keycorresponding to the first connector port and a second connector keycorresponding to the second connector port, the first and secondconnector keys having different configurations from one another.

According to some aspects, a fiber optic connection system includes afiber optic adapter defining an adapter axis. The fiber optic adapterdefines a first connector port aligned along the adapter axis and alsodefines a second connector port aligned along the adapter axis. Thefirst connector port has an open end that faces in a first axialdirection. The second connector port has an open end that faces in asecond axial direction. A first ferrule-less fiber optic connector isconfigured to be received in the first connector port and a secondferrule-less fiber optic connector is configured to be received in thesecond connector port. The second ferrule-less fiber optic connector isconfigured to accommodate more fiber buckling than the firstferrule-less fiber optic connector.

In some aspects, the fiber optic connector is provided with a connectorbody defining a fiber buckling zone within an interior of the connectorbody; a connector tip positioned at one end of the connector body. Theconnector body is movable relative to the connector tip between firstand second axial positions along an axis that extends through the firstbuckling zone. An optical fiber that extends through the fiber bucklingzone and through the connector tip has a free end that protrudes beyondthe connector tip in a direction away from the buckling zone. The freeend of the optical fiber is not supported by a ferrule. The opticalfiber is axially moveable relative to the connector tip. A fiberbuckling controller is positioned at the fiber buckling zone, the fiberbuckling controller including a flex member that elastically flexes froma first flex position to a second flex position as the connector bodymoves between the first and second axial positions relative to theconnector tip. The flex member has a sharper curvature in the secondflex position as compared to the first flex position, and is configuredto positively force the optical fiber to buckle within the buckling zoneas the flex member moves from the first flex position to the second flexposition.

According to some aspects, the fiber optic adapter is provided with anadapter body defining an adapter axis, the adapter body defining a firstconnector port and a second connector port aligned along the adapteraxis. A fiber alignment structure is mounted within the adapter body.The first and second connector ports each have a lead-in section fordirecting a free end portion of an optical fiber of a ferrule-less fiberoptic connector into the fiber alignment structure, the lead-in sectionhaving a tapered fiber passage profile including: a) a first axialtransition portion having a first passage section that tapers radiallyoutwardly away from the adapter axis as the first axial transitionportion extends axially toward the fiber alignment structure; and b) asecond axial transition portion positioned axially between the firstaxial transition portion and the fiber alignment structure, the secondaxial transition portion having a second passage section that tapersradially inwardly toward the adapter axis as the second axial transitionportion extends axially toward the fiber alignment structure.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the description, illustrate several aspects of the presentdisclosure. A brief description of the drawings is as follows:

FIG. 1 is a perspective view of an example prior art ferrule-lessoptical connector.

FIG. 2 is a perspective view of an exemplary optical connector.

FIGS. 3A-3D show a system including the optical connector of FIG. 2aligned with and/or inserted into a port of an example optical adapter.

FIG. 4A is a perspective view of a prior art optical fiber alignmentdevice.

FIG. 4B is an end view of the optical fiber alignment device of FIG. 4A.

FIG. 4C is a longitudinal cross-sectional view of the optical fiberalignment device of FIG. 4B taken along section line 4C-4C.

FIG. 4D is an exploded view of the optical fiber alignment device ofFIG. 4A.

FIG. 4E is a longitudinal cross section of FIG. 4C with the internalcomponents removed.

FIG. 4F is a transverse cross section of the optical fiber alignmentdevice of FIG. 4A.

FIG. 5 is a longitudinal cross section of a fiber optic adapter with twooptical connector plugs and an optical fiber alignment device connectingoptical fibers.

FIGS. 6A-6D are graphical presentations of results from a measurement ofoptical loss across an optical alignment device.

FIG. 7A is a top plan view of an optical fiber alignment device inaccordance with the principles of the present disclosure.

FIG. 7B is a top view of the optical fiber alignment device of FIG. 7Awith the biasing arrangement removed.

FIG. 7C is a perspective view of the optical fiber alignment device ofFIG. 7A.

FIG. 7D is a transverse cross section of the optical fiber alignmentdevice of FIG. 7A.

FIG. 7E is a longitudinal cross section of the optical fiber alignmentdevice of FIG. 7D along section line 7E-7E.

FIG. 8A is a top plan view of an optical fiber alignment device inaccordance with the principles of the present disclosure.

FIG. 8B is a top view of the optical fiber alignment device of FIG. 8Awith the biasing arrangement removed.

FIG. 8C is a perspective view of the optical fiber alignment device ofFIG. 8A.

FIG. 8D is a transverse cross section of the optical fiber alignmentdevice of FIG. 8A.

FIG. 8E is a longitudinal cross section of the optical fiber alignmentdevice of FIG. 8D along section line 8E-8E.

FIG. 9A is a top plan view of an optical fiber alignment device inaccordance with the principles of the present disclosure.

FIG. 9B is a top view of the optical fiber alignment device of FIG. 9Awith the biasing arrangement removed.

FIG. 9C is a perspective view of the optical fiber alignment device ofFIG. 9A.

FIG. 9D is a transverse cross section of the optical fiber alignmentdevice of FIG. 9A.

FIG. 9E is a longitudinal cross section of the optical fiber alignmentdevice of FIG. 9D along section line 9E-9E.

FIG. 10A is a side view of a prior art shutter for an optical connector.

FIG. 10B is a back view of the shutter of FIG. 10A.

FIG. 11A is an axial cross section of an optical connector including ashutter.

FIG. 11B is a detail of the shutter in FIG. 11A.

FIGS. 12A-12C are schematic depictions of the path of a light ray froman optical fiber.

FIG. 13 is a schematic depiction of the path of a light ray from anoptical fiber in a prior art system.

FIG. 14 is a schematic depiction of the path of a light ray from anoptical fiber in a system in accordance with the principles of thepresent disclosure.

FIG. 15A is a perspective view of a shutter for an optical connector inaccordance with the principles of the present disclosure.

FIG. 15B is a back perspective view of the shutter of FIG. 15A.

FIG. 15C is a front view of the shutter of FIG. 15A.

FIG. 15D is a top view of the shutter of FIG. 15A.

FIG. 15E is a side view of the shutter of FIG. 15A.

FIG. 15F is a bottom view of the shutter of FIG. 15A.

FIG. 15G is a cross-sectional view of the shutter of FIG. 15A takenalong section line 15G-15G.

FIG. 15H is a detail view of the shutter of FIG. 15G.

FIG. 15J is a back view of the shutter of FIG. 15A.

FIG. 15K is a schematic depiction of the cross section of the insidesurface of the shutter of FIG. 15A.

FIG. 16A is a side view of a biasing spring in accordance with theprinciples of the present disclosure.

FIG. 16B is a perspective view of a cross section of an opticalconnector plug with the biasing spring of FIG. 16A.

FIGS. 17A-17D are sequential diagrammatic views of the optical connectorplug of FIG. 16B as the optical connector plug is inserted into anoptical adapter in accordance with the principles of the presentdisclosure.

FIG. 18 is a cross sectional top view of a fiber alignment device inaccordance with the principles of the present disclosure having a fiberbiasing member laterally offset from an alignment groove.

FIG. 19 is a top view of two halves of a fiber optic adapter with atapered lead-in section in accordance with the principles of the presentdisclosure for directing optical fibers into a fiber alignment structurehoused within a housing of the adapter.

FIGS. 20A-20D are graphical presentations of the results from Example 1.

FIG. 21 is an axial cross sectional view of a fiber optic adapter inaccordance with the principles of the present disclosure.

FIG. 22A is a back view of a shutter for an optical connector inaccordance with the principles of the present disclosure.

FIG. 22B is back perspective view of the shutter of FIG. 22A.

FIG. 22C is a cross-sectional view of the shutter of FIG. 22A with anoptical fiber tip positioned therein.

FIG. 23A is a back view of a shutter for an optical connector inaccordance with the principles of the present disclosure.

FIG. 23B is back perspective view of the shutter of FIG. 23A.

FIG. 23C is a cross-sectional view of the shutter of FIG. 23A with anoptical fiber.

FIG. 24A is a back view of a shutter for an optical connector inaccordance with the principles of the present disclosure.

FIG. 24B is back perspective view of the shutter of FIG. 24A.

FIG. 24C is a cross-sectional view of the shutter of FIG. 24A with anoptical fiber.

FIG. 25A is a back view of a shutter for an optical connector inaccordance with the principles of the present disclosure.

FIG. 25B is back perspective view of the shutter of FIG. 25A.

FIG. 25C is a cross-sectional view of the shutter of FIG. 25A with anoptical fiber.

DETAILED DESCRIPTION

The present disclosure relates generally to fiber optic adapters, fiberoptic connectors and systems including fiber optic adapters for use inoptically coupling fiber optic connectors together. In preferredexamples, the fiber optic connectors are ferrule-less (i.e., includefiber ends that are free and not supported by ferrules) and the fiberoptic adapters are configured for co-axially aligning bare opticalfibers. Aspects also relate to connectors having enhanced shutterconfigurations for protecting optical fibers.

The term “fiber” as used herein can relate to an optical signaltransmission element. In certain examples, the fiber can include a corehaving a diameter of 8-12 μm and a cladding having a diameter of 120-130μm, wherein the core is the central, light-transmitting region of thefiber, and the cladding is the material surrounding the core forming aguiding structure for light propagation within the core. The core andcladding can be coated with a primary coating usually comprising one ormore organic or polymer layers surrounding the cladding to providemechanical and environmental protection to the light-transmittingregion. The primary coating may have a diameter ranging, e.g., between200 and 300 μm. The core, cladding and primary coating may also becoated with a secondary coating, a so-called “buffer,” a protectivepolymer layer without optical properties applied over the primarycoating. The buffer or secondary coating usually has a diameter rangingbetween 300-1100 μm, depending on the manufacturer. It will beappreciated that aspects of the present disclosure also apply to opticalfibers having dimensions other than those specifically recited.

The term “light” as used herein relates to electromagnetic radiation,which comprises a part of the electromagnetic spectrum that isclassified by wavelength into infrared, the visible region, andultraviolet.

Index matching gel can be used with alignment devices in accordance withthe principles of the present disclosure to improve the opticalconnection between the open light transmission paths of the first andsecond optical fibers (e.g., to reduce loss that may otherwise occur atair gaps between the fiber end faces). The index matching gel preferablyhas an index of refraction that closely approximates that of an opticalfiber. The index matching gel is used to reduce Fresnel reflection atthe surface of the bare optical fiber ends. Without the use of anindex-matching material, Fresnel reflections will occur at the smoothend faces of a fiber and reduce the efficiency of the optical connectionand thus of the entire optical circuit.

Reference will now be made in detail to exemplary aspects of the presentdisclosure that are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

The present disclosure relates generally to fiber optic connectors andadapters. FIGS. 2 and 3A-3D illustrate example fiber optic connectors300 and adapters 100. The fiber optic connectors 300 each include aconnector plug body 322 and a latch arm 330 for securing the connectorplug body 322 to a port in a corresponding fiber optic adapter 100(FIGS. 3A-3D). The connector plug body 322 includes a front end 324positioned opposite from a rear end 326 (FIG. 2 ). The front end 324 ofthe connector body 322 is configured to provide access to an end 109 ofan optical fiber 108 that extends through the connector body 322 (see,e.g., FIG. 3B).

The latch arm 330 is configured to secure the connector plug body 322 toa corresponding fiber optic adapter 100 (see, e.g., FIGS. 3B and 3C).The latch arm 330 is connected to the plug body 322 at a flexible pivotlocation that allows the latch arm 330 to be pivoted (i.e., flexed)relative to the connector plug body 322 between a latching position anda release position. The adapter 100 may include corresponding latchingmembers constructed to mate with a latch end of the latch arm 330.

In some implementations, the fiber optic connector 300 includes aplurality of ribs 335 that extend outwardly from the plug connector body322 for providing extra strength to the fiber optic connector body 322or for inhibiting manual or accidental opening of a shutter 328 by auser. The shutter 328 pivots open and shut relative to the connectorbody 322 to expose and cover, respectively, the optical fiber tip 109when tabs 329 of the shutter 328 are deflected. In use, the tabs 329 aredeflected by lugs within the adapter 100. The ribs 335 inhibit fingeraccess to the shutter tabs 329 to hinder opening of the shutter 328outside of the adapter 100 (e.g., accidental opening, unauthorizedopening, etc.).

FIG. 3A depicts the fiber optic connector 300 aligned with a first port110 of an example optical adapter 100. A body 150 of the optical adapter100 includes opposite sidewalls 155 extending along a height H150 of thebody 150 between opposite top 152 and bottom 153. The sidewalls 155 alsoextend along a length L150 of the body 150 between a first end 157 and asecond end 158. The body 150 defines a first port 110 at the first end157. In certain examples, the body 150 defines a second port 120 at thesecond end 158 that is aligned with the first port 110 along aninsertion axis I. In certain examples, the body 150 can define a greaternumber of ports 110, 120.

When the connectors 300 are inserted into the first port 110 and thesecond port 120 of the adapter 100 along the insertion axis I, theshutters 328 of the connectors 300 retract (i.e., pivot open) and exposethe ends 109 of the optical fibers 108 (see FIGS. 3A-3D). The adapterbody 150 houses an alignment structure 200 for aligning the ends 109.Continued insertion of the connectors 300 into the first and secondports 110, 120 causes the ends 109 to enter the alignment structure 200.FIGS. 3C and 3D show both connectors 300 inserted all the way into theadapter 100 and secured into place by latches 330.

The alignment structure 200 is configured to align optical fibers 108 ofoptical connectors 300 received at the ports 110, 120. An example of analignment device is disclosed in U.S. patent application Ser. No.14/377,189 issued as U.S. Pat. No. 9,575,263, which documents areincorporated herein by reference. The alignment device generallyincludes an alignment housing with the fiber insertion axis extendingthrough the alignment housing and structures for aligning the opticalfibers along the fiber insertion axis. The structures may provide afiber alignment groove extending along the fiber insertion axis, andfiber biasing members opposing the fiber alignment groove for pressingoptical fibers into the fiber alignment groove. The fiber alignmentgroove can generally be defined as a groove in a plate or otherstructure, having a V-shaped, rounded, U-shaped, or other crosssectional shape, or may be defined between parallel rods.

FIGS. 4A-4F illustrate a prior art optical fiber alignment device 420that includes two alignment rods with rounded ends to provide a fiberalignment groove or slot, and two biasing or alignment members (e.g.,two balls) that act to align the fiber in the fiber alignment slot. Thealignment housing 424 includes first and second ends 426, 428, and afiber insertion axis 422 that extends through the alignment housing 424between the first and second ends 426, 428. The alignment housing 424has a main body 429 that is elongated between the first and second ends426, 428 and that includes an outer shape 431 that is cylindrical. Thealignment housing 424 also includes a longitudinal rib 430 that projectslaterally outwardly from the outer shape 431 of the main body 429 of thealignment housing 424.

The alignment housing 424 defines an internal chamber 432. The internalchamber 432 extends completely through the length of the alignmenthousing 424 from the first end 426 to the second end 428. In this way,optical fibers can be inserted along the fiber insertion axis 422through the alignment housing 424. The internal chamber 432 includes anelongated access slot 434 having a length L1 (See FIG. 4E), a depth D1and a width W1 (see FIG. 4F). The length L1 extends along the length ofthe alignment housing 424. The depth D1 extends laterally (i.e.,radially) into the alignment housing 424. The width W1 is transversewith respect to the depth D1 and the length L1. The prior art alignmentdevice 420 shown in FIGS. 4A-4D includes two fiber biasing members(e.g., balls). The internal chamber 432 also includes first and secondball-receiving pockets 436, 438 positioned along the length L1 of theelongated access slot 434. The first and second ball-receiving pockets436, 438 each have a width W2 (see FIG. 4F) that is larger than thewidth W1 of the elongated access slot 434. The first and secondball-receiving pockets 436,438 have depths D2 (see FIG. 4F) that areparallel to the depth D1 of the elongated access slot 434. The first andsecond ball-receiving pockets 436,438 each include cylindricalpocket-defining surfaces 440 (see FIG. 4D) that extend partially aroundball insertion axes 442 (see FIG. 4E) that are parallel to the depthsD2. The pocket-defining surfaces 440 of each of the pockets 436,438 arepositioned on opposite sides of the elongated access slot 434. Thepocket-defining surfaces 440 of the first ball-receiving pocket 436oppose one another, and the pocket-defining surfaces 440 of the secondball-receiving pocket 438 oppose one another. The first and secondball-receiving pockets 436, 438 also include ball seats 444 positionedat opposite sides of the elongated access slot 434. It will beappreciated that one ball seat 444 corresponds to each of thepocket-defining surfaces 440. The ball-seats are located at bottom endsof the first and second ball-receiving pockets 436, 438.

The internal chamber 432 also includes a rod-receiving region 450 at thebottom of the depth D1 of the elongated access slot 434. Therod-receiving region 450 has a width W3 that is larger than the width W1of the elongated access slot 434. The rod receiving region 450 extendsgenerally along the entire length of the alignment housing 424.

The optical fiber alignment device 420 also includes first and secondalignment rods 452, 454 (see FIG. 4D) that fit within the rod-receivingregion 450 of the alignment housing 424. The first and second alignmentrods 452,454 mount parallel to one another within the rod-receivingregion 450 and can be inserted into the rod-receiving region 450 throughthe elongated access slot 434. Each of the first and second alignmentrods 452, 454 includes an intermediate section 456 that is generallycylindrical in shape. Each of the first and second alignment rods 452,454 also has rounded ends 458. In the example shown, the rounded ends458 are spherical in shape and form semi-spheres. The intermediatesections 456 of the first and second alignment rods 452, 454 cooperateto define a fiber alignment slot 460 that extends along the fiberinsertion axis 422 through the alignment housing 424. The rounded ends458 are positioned adjacent the first and second ends 426, 428 of thealignment housing 424. The alignment housing 424 defines partial funnelstructures 462 positioned at the first and second ends 426, 428. Thepartial funnel structures 462 are positioned above the rounded ends 458of the first and second alignment rods 452, 454. The partial funnelstructures 462 form a tapered transition that angles toward the fiberinsertion axis 422 and the fiber alignment slot 460. The partial funnelstructures 462 cooperate with the rounded ends 458 of the first andsecond alignment rods 454, 456 to define a tapered lead-in structure forguiding optical fibers toward the fiber insertion axis 422.

The optical fiber alignment device 420 is configured for opticallyaligning the ends of two optical fibers desired to be mechanically andoptically connected together. The optical fiber alignment device 420further includes structure for urging the optical fibers desired to beoptically connected together into contact with the fiber alignment slot460 defined by the fiber alignment rods 452, 454. In the example shownin FIGS. 4A-4D, the fiber optical alignment device 420 includes firstand second balls 470, 471 (i.e., fiber biasing members) positionedrespectively within the first and second ball-receiving pockets 436,438. The balls 470, 471 are depicted as being spherical in shape. Wheninserted within their corresponding first and second ball-receivingpockets 436, 438, the first and second balls 470, 471 seat against theball seats 444. Lower portions of the first and second balls 470, 471extend downwardly into the rod-receiving region 450 and are alignedalong the fiber alignment slot 460 and the fiber insertion axis 422. Thepocket defining surfaces 440 surround portions of the balls 470,471 andmaintain alignment of the balls 470, 471 with their respective ballinsertion axes 442. In certain examples, the ball insertion axes 442intersect the fiber insertion access 422 and the fiber alignment slot460.

The optical fiber alignment device 420 further includes a biasingarrangement for urging the balls 470, 471 generally toward the fiberalignment slot 460. For example, the biasing arrangement can urge theballs 470, 471 in a direction transverse with respect to the fiberinsertion axis 422. In the example shown, the biasing arrangement isshown including a clip 472 (e.g., a metal clip having elasticproperties) mounted (e.g., snap fitted) over the main body 429 of thealignment housing 424. The clip 472 can have a transversecross-sectional profile that is generally C-shaped. Ends 474 of the clipcan abut against sides of the longitudinal rib 430 of the alignmenthousing 424. When the clip 472 is snapped or otherwise fitted over thealignment housing 424, the clip 472 functions to capture the first andsecond balls 470, 471 within their respective first and secondball-receiving pockets 436, 438. The clip 472 can include biasingstructures such as first and second springs 476, 478 for respectivelybiasing the balls 470, 471 toward the fiber alignment slot 460. Asdepicted, the first and second springs 476, 478 are leaf springs havinga cantilevered configuration with a base end integrally formed with amain body of the clip 472 and free ends that are not connected to themain body of the clip 472. In the example shown, the first and secondsprings 476, 478 both extend from their base ends to their free ends inthe same rotational direction about the fiber insertion axis 422. Thesprings 476, 478 are defined by cutting or slitting the main body of theclip 472 so as to define slots in the main body of the clip 472 thatsurround three sides of each of the springs 476, 478.

In use of the optical fiber alignment device 420, two optical fibersdesired to be optically connected together are inserted into the firstand second ends 426, 428 of the alignment housing 424. As the opticalfibers are inserted into the first and second ends 426, 428, the partialfunnel structure 462 and the rounded ends 458 of the first and secondalignment rods 452, 454 cooperate to guide the ends of the optical fibertoward the fiber insertion axis 422. Continued insertion of the opticalfibers causes the optical fibers to move along the fiber alignment slot460 defined by the intermediate sections 456 of the first and secondalignment rods 452, 454. As the optic fibers move along the fiberalignment slot 460, the optical fibers force their corresponding balls470, 471 away from the fiber alignment slot 460 against the bias of thesprings 476, 478. The optical fibers slide along the fiber alignmentslot 460 until the end faces of the optical fibers are optically coupledto one another. In this configuration, the first and second spring 476,478 and the first and second balls 470, 471 function to clamp orotherwise retain the optical fibers in the optically coupled orientationwithin the fiber alignment slot 460. In this way, the optical fibers arepressed within the fiber alignment slot 460 by the first and secondballs 470, 471 such that axial alignment between the optical fibers ismaintained.

Upon insertion of the connectors in the adapter, the fiber ends 109 abutcausing an axial load to be applied to the fibers which causes thefibers to buckle within the connector bodies (see FIG. 5 ). The opticalfibers 108 are placed in the connector 300 so that the fibers protrudepast the center line within the alignment structure 200 to ensurecontact between the two optical fibers 108. However, uncontrolledbuckling of the optical fibers 108 can result in undesired variabilityin light transfer. Further, if the optical fibers 108 protrude too far(e.g., about 200 μm or more), the increased buckling may result in anincreased loss in light transfer.

To demonstrate the dependence of optical loss as a function of overlap,connectors 300 were arranged with varying degrees of fiber tip overlapand the optical loss was measured. FIGS. 6A-6D are graphicalpresentations of the loss in dB as a function of the position of themating interface relative to the center along the optical axis of thefiber (Z-axis) with 20 μm overlap (FIG. 6A), 120 μm overlap (FIG. 6B),360 μm overlap (FIG. 6C), and 600 μm overlap (FIG. 6D). As demonstratedby the test results, the loss in light transfer varied as a function ofthe overlap. However, the range of overlap with minimal loss is small,about 300-400 μm, which may explain some of the issues with variance inoptical loss. Controlling the amount of overlap within a range of about100 μm is technically difficult and requires great precision inassembly. Such a narrow optimal range makes the connector assemblyvulnerable to optical losses due to possible errors during assembly orirregularities in materials.

In order to increase tolerance in the direction of the optical axis, thefiber alignment structure 200 can house an alignment device 220 thatprovides more contact points between the fiber biasing member(s) and thefibers 108 in the fiber alignment groove 105. For example, the alignmentdevice 220 can be provided with three or more (e.g., four, five, six, ormore) fiber biasing members that may be biased toward the fiberalignment groove 105 by a spring. In some embodiments, the alignmentdevice 220A, 220B includes first and second fiber biasing members 270,271, and a third fiber biasing member 272 positioned between the firstand second fiber biasing members 270, 271. The third fiber biasingmember 272 may be positioned at a mid-point between the first and secondfiber biasing members 270, 271, or at a transition between a firstportion of the fiber alignment groove 105 and a second portion of thefiber alignment groove 105. In some embodiments, the fiber alignmentdevice 220 includes four or more discrete fiber biasing members. Forexample, the fiber alignment device 220 may include first and secondfiber biasing members positioned opposite of the first portion of thefiber alignment groove 105, and third and fourth fiber biasing membersopposite of the second portion of the fiber alignment groove 105.

The fiber biasing members may have any suitable shape, such as balls,spheres, semi-spheres, rods, or rounded cuboids. The fiber biasingmembers may also be provided as one or more elastic cantilevers. In theembodiments shown in FIGS. 7A-7E and 8A-8E, the fiber biasing memberscomprise first, second, and third balls 270, 271, 272, where the thirdball is positioned between the first and second balls at a midpoint ofthe fiber alignment device 220. The alignment device 220 is not limitedto only two or three fiber biasing members (e.g., balls), but mayinclude four or more fiber biasing members. The fiber biasing membersmay also have different shapes, such as semi-spheres, rods, or roundedcuboid shapes. The fiber biasing members may also be shaped as a rod(e.g., one or more fiber contact rods 273) extending the length of theelongated access slot 234, as shown in FIGS. 9A-9E. The alignmenthousing 224 and biasing arrangement can be adjusted accordingly.

In some aspects, the elongated access slot 234 is provided withball-receiving pockets 235, as shown in FIGS. 7A-7C. The ball-receivingpockets 235 can have a shape that generally follows the contour of thefiber biasing members (e.g., first, second, and third balls 270, 271,272). For example, as shown in FIGS. 7A-7C, the ball-receiving pockets235 have an inside wall 240 that is curved to accommodate the balls.However, the elongated access slot 234 may also be constructed withstraight side walls 241 to receive either a plurality of fiber contactmembers, as in FIGS. 8A-8C, or a single fiber contact rod 273, as inFIGS. 9A-9C.

The biasing arrangement is shown including a clip 274 (e.g., a metalclip having elastic properties) mounted (e.g., snap fitted) over thealignment housing 224. The clip 274 can have a transversecross-sectional profile that is generally C-shaped. For example, if thebiasing members comprise first, second, and third balls 270, 271, 272,the biasing arrangement may correspondingly include first, second, andthird springs 276, 278, 279. If the biasing member comprises a singlefiber contact rod 273, the biasing arrangement may include either aplurality of springs (e.g., as shown in FIG. 9A), or may include asingle spring.

Shutter

In general, it is desired that both light loss across the adapter andvariability in the light loss are minimized when the fibers areconnected using connectors. However, when the connector is unconnected,it is desirable that little or no light is reflected back into thefiber. The amount of light reflected by a fiber-optic connector is knownas the return loss of the connector, and is typically measured in unitsof dB. For example, if 1% of light is reflected back, then thereflectance is R=0.01 and the return loss is RL=−10 log(R)=+20 dB. It isdesirable to have the return loss of an unconnected plug be 50 to 70 dB,with higher values of return loss preferred. In some aspects the fiberoptic connector can be provided with a shutter that, when in a closedposition, reduces the return of light through the fiber in anunconnected connector plug.

In a typical prior art shutter 15, shown in FIGS. 10A and 10B, theforward-facing shutter wall 20 has an inside surface 21 with a planarcenter portion 22. The planar center portion 22 can be surrounded byrounded edges, forming a bowl-shape interior receptacle that may containan index matching gel used to protect and clean the fiber when theshutter 15 is closed. As seen in cross-sectional FIGS. 11A and 11B, thefree end of the optical fiber 108 is received by the interior receptacleand is located close to the inside surface of the shutter when theshutter 15 is in a closed position. The distance from the tip of theoptical fiber 108 to the shutter is nominally about 0.15 mm. With thefiber tip located close to the inside surface 21 of the shutter 15, arelatively large amount of light reflected back from the closed shutter15 can re-enter the optical fiber 108 when the connector plug is notconnected.

Simplified depictions of the tip of an optical fiber 108 pointed at theinside surface 21, 541 of the shutter 15, 528, are shown in FIGS.12A-12C, 13, and 14 , showing a single “ray” of light. If the tip of theoptical fiber 108 is cut flat (perpendicular to the optical axis of thefiber) as in FIG. 12A, light from the fiber reflects back into theoptical fiber 108 from the inside surface 21. Although the intensity ofthe reflected light is reduced due to the finite reflectivity of theshutter's inside surface, it is desired to reduce the amount ofreflected light (i.e., to increase the return loss). Fiber tips aretypically cut at an angle of about 8°, as shown in FIGS. 12B and 12C(the angles are exaggerated for demonstration purposes). When the angledtip is in air, as in FIG. 12B, the light will bend and reflect away fromthe optical fiber 108. However, when the tip is embedded in indexmatching gel 26 with an index of refraction that matches the index ofrefraction of the fiber, the light travels straight and again reflectsback into the optical fiber 108, as shown in FIG. 12C.

In some fiber optic connectors, this problem has been solved by anangled inside surface 21′ of the shutter, as shown schematically in FIG.13 . The angled inside surface 21′ increases the return loss, thuspreventing most of the light from returning back into the fiber.However, a disadvantage of the angled surface is that the shutter wallis much thicker at one side (top in FIG. 13 ) relative to the other side(bottom in FIG. 13 ). Further, the solution of a single angled insidesurface 21′ cannot be implemented in a shutter where the gap between thefiber and the shutter is only 0.15 mm. In other cases, a non-uniformwall thickness may cause excessive “sink” when the shutter surface ismolded. This sink is a localized deformation of the surface which mayact as a lens, focusing the light back on the fiber, thereby causingundesirably high light return.

According to an aspect of the present disclosure shown in FIGS. 14, 15B,15G, 15H, and 15J, the inside surface 541 of the shutter wall 540includes a light distribution structure with a plurality (or series) ofangled facets 542 a, 542 b. The facet surfaces are angled relative toone another. When the shutter is closed, the fiber axis intersects thelight distribution structure. As a result, the light is reflected backat an angle, causing a high return loss, while the thickness T540 of theshutter wall 540 can be kept from getting too thick. In one embodiment,the texture on the inside surface of the shutter consists of a series offlat surfaces (facets 542 a, 542 b) which are arranged in aconfiguration that has the appearance of a “washboard,” or a “saw tooth”in cross-section (see FIGS. 14, 15G, and 15H). As compared to the singleangled surface of FIG. 13 , the thickness T542 of the faceted portion542 (see FIG. 15K) is reduced by a factor of 4, while retaining thefunctionality of the angled feature.

The angle β of the facets 542 a, 542 b, and the thickness T542 of thefaceted portion 542 can be adjusted to minimize light reflected backwithin limitations of the fabrication method used to produce the shutter528. The angle β and thickness T542 can also be adjusted to provide alow-profile shutter wall 540 having a relatively low wall thicknessT540. The angle β of the facets 542 a, 542 b in the series of facets canalso vary such that different facets have different angles. In apreferred embodiment, the facets surfaces are smooth to minimize lightscattering, and the corners between the facet surfaces are sharp.However, due to limitations of materials and fabrication methods, someroughness of the surfaces and rounding of the corners inevitably occurs,resulting in a trade-off between a more uniform thickness T540 of theshutter wall 540 and reduction in the return loss.

The facets 542 a, 542 b can be arranged in substantially vertical,parallel lines, as shown in the example in FIGS. 15B and 15J. However,many other possible configurations exist, such as parallel linesarranged at a non-vertical angle (e.g., horizontal, diagonal, or anyother angle), or facets arranged in the shape of tetrahedrons orpyramids, or arranged in concentric circles or other concentric shapes.The fabrication method will, in some cases, dictate the type of surfacewhich can be formed at a reasonable cost.

The shutter 528 can be constructed out of any suitable material. Oneexample of a suitable material is molded plastic (e.g., an engineeringplastic). The parallel lines shown in FIGS. 15B and 15J can be createdin the mold steel using grinding. More complex features can be createdusing diamond-turning, which is a more expensive process. Chemicaletching may also be employed to create angled features in either themold steel or in the finished part. Shutter 528 may be constructed withtabs 529.

In some implementations, the faceted portion 542 has a thickness T542 ofabout 0.001 to 1 mm, or about 0.01 to 0.5 mm. The thickness T542 of thefaceted portion 542 is preferably less than the thickness T540 of thewall 540. For example, the thickness T542 of the faceted portion 542 canbe about half, about ⅓, about ¼, about ⅕, about 1/10, or from about ½ toabout 1/20 of the thickness T540 of the wall 540. The faceted portion542 can extend throughout the planar center portion of the insidesurface 541, of can be provided in a center part of the planar centerportion only. For example, the faceted portion 542 can be provided in anarea where light from the optical fiber 108 is expected to hit theinside surface 541.

The facets 542 a, 542 b can be disposed at an angle β of about 5° to45°, about 8° to 30°, about 10° to 20°, about 12° to 16°, or any numbertherebetween. The angle β is measured as the angle of the facets 542 a,542 b relative to a plane perpendicular to the optical axis of the fiber108. A higher return loss can be achieved with a greater angle β.

According to some aspects, the inside surface 541 of the shutter wall540 includes a fiber guiding structure 550 that receives the tip of theoptical fiber 108 and guides the end portion of the optical fiber 108into an angle relative to the axis of the connector. In someembodiments, the fiber guiding structure 550 can be formed as a cut-outor a groove on the planar center portion 522 of the shutter wall 540.Exemplary fiber guiding structures 550 are shown in FIGS. 22A-25C. Inone embodiment shown in FIGS. 22A-22C, the fiber guiding structure 550comprises a guiding portion 554 and a tip-receiving portion 557. Theguiding portion 554 and the tip-receiving portion 557 are part of anintegrated depression (e.g., a cut out) in the planar center portion522. The tip-receiving portion 557 is positioned at a distance from thecenter C522 of the planar center portion 522 as shown in FIG. 22A. Forexample, the tip-receiving portion 557 can be positioned about 10 toabout 90% of the way from the center C522 toward an edge 523 of theplanar center portion 522, or about 20 to about 50% of the way from thecenter C522 toward the edge 523. The fiber guiding structure 550 and thetip-receiving portion 557 can be disposed on any side of the center C522(e.g., below, above, or on one side). In the examples shown, the fiberguiding structure 550 and the tip-receiving portion 557 are positionedbelow the center C522. The fiber guiding structure 550 has a back wall551 and sloping side walls that lead into the tip-receiving portion 557.The back wall 551 of the guiding portion 554 may be flat orperpendicular to the axis of the connector 300, or may include a slopingsection 555 that helps to guide the tip of the fiber 108 into thetip-receiving portion 557. In the tip-receiving portion 557 the backwall 551 may include one or more angled facets that reflect the lightfrom the tip of the fiber 108 away from the fiber 108. For example, theback wall 551 may include a single angled facet 559. The tip-receivingportion 557 has side walls (e.g., a curved side wall, as shown) thatpartially circumscribe the tip of the fiber 108.

In one embodiment shown in FIGS. 23A-23C, the fiber guiding structure550 does not include a separate tip-receiving portion, but rather, theguiding portion 554 terminates in a corner 562 where the tip of theoptical fiber 108 is received. In another embodiment shown in FIGS.24A-24C, the tip-receiving portion 557 comprises a groove 564 thatextends from the guiding portion 554 to the opposite edge 523 of theplanar center portion 522. The back wall 551 in the groove 564 mayinclude a single angled facet 559 for directing the light from theoptical fiber 108. Yet another embodiment of the fiber guiding structure550 is shown in FIGS. 25A-25C, where the fiber guiding structure 550includes a single groove 566 with faceted side walls 568 and top andbottom walls 569, where the groove 566 extends from one edge of theplanar center portion at least partially to an opposite edge of theplanar center portion.

Providing the shutter 528 with a fiber guiding structure 550 helpscapture the position of the optical fiber 108 tip and can help point thetip toward a faceted surface at a specific angle. Further, a fewernumber of facets (e.g., a single facet or two facets) is easier tomanufacture than a large number of facets, thus resulting in a moreconsistent and reliable product. Because of the smaller facet surfaceand the indented structure, the fiber guiding structure 550 does not addor only adds minimally to the thickness of the wall 540. In theembodiments where the end portion of the optical fiber 108 is bent bythe tip-receiving portion 557, a very shallow angle of the back wall 551is sufficient to divert the light coming from the optical fiber 108,further reducing the need for added thickness. For example, the backwall 551 may have an angle of about 3° to 45°, about 4° to 30°, about 5°to 20°, about 5° to 10°, or any number therebetween. The fiber guidingstructure 550 also reduces the amount of index matching gel neededbecause the gel can be provided only in the fiber guiding structure 550and does not need to cover the whole area of the planar center portion522.

Fiber Buckling

Optical losses and variance in the adapter system can be further reducedby controlling the direction of buckling of the fiber 108.

According to some aspects, the fiber optic adapter 100 can be arrangedsuch that one of the fiber optic connectors 300 is installed first in afirst connector port 110, and the second fiber optic connector 302 isinstalled second in a second connector port 120, where the adapter 100and connectors 301, 302 are constructed so that buckling only happens inone of the connectors 300. This can be done, for example, by controllingthe order of installation of the connectors, or by altering the geometryof the connectors. For example, the first fiber optic connector 301 canbe installed without buckling, and the second fiber optic connector 302installed after the first fiber optic connector 301 so that bucklingonly occurs in the second fiber optic connector 302.

The fiber optic adapter 100 can be labelled to indicate which sideshould be installed first, for example, by including text (e.g., “first”and “second”) or a numeric indication (e.g., “1” and “2”) by the firstand second ports 110, 120. The fiber optic adapter 100 may also beconstructed to include a mechanism that prevents a second fiber opticconnector 300 from being installed in the second connector port 120before the first fiber optic connector 300 is installed in the firstport 110. For example, the fiber optic adapter 100 can include a latchor other mechanism that protrudes into the second connector port 120 butmoves out of the way when the first fiber optic connector 300 isinstalled. In one embodiment, the fiber optic adapter 100 has a firstconnector key corresponding to the first fiber optic connector, and asecond connector key corresponding to the second fiber optic connector,such that the first and second fiber optic connectors can only beinstalled in their corresponding ports 110, 120. For example, the portopening can have a shape that corresponds to the respective connector,and is different for the first and second fiber optic connectors. Whenthe order of installation is controlled, also buckling can be controlledso that buckling only occurs in one of the fiber optic connectors. Thefirst and second connector ports 110, 120 and the fiber alignmentstructure can also be configured to accommodate single fiberferrule-less fiber optic connectors.

Fiber buckling can also be controlled by constructing the fiber opticconnectors 300 so that one of the fiber optic connectors can accommodatemore buckling than the other. For example, one of the fiber opticconnectors (e.g., the first fiber optic connector) can have an axiallength that is shorter than the axial length of the other fiber opticconnector (e.g., the second fiber optic connector). Further, one of thefiber optic connectors can be constructed so that it accommodates nofiber buckling or very minimal fiber buckling.

In one example, the fiber optic adapter 100′ is constructed so that theposition of the alignment device 220 is offset in the axial direction,as shown in FIG. 21 . In the example, the adapter body 101′ defines anadapter axis A101′, and the adapter body 101′ is bisected by a firstreference plane P101′ that is perpendicular relative to the adapter axisA101′. A fiber alignment groove 105 extends axially through at least aportion of the adapter body 101′. The fiber alignment groove 105 has anopen side that extends axially along the groove. The adapter body 101′also defines a first connector port 110 and a second connector port 120,each aligned along the adapter axis, and the first connector port 110having an open end that faces in a first axial direction and the secondconnector port 120 having an open end that faces in a second axialdirection. A first portion of the fiber alignment groove 105 correspondsto the first connector port and a second portion corresponds to thesecond connector port. The fiber alignment structure 220 is mountedwithin the adapter body 101′ such that a second reference plane P220that bisects the fiber alignment structure 220 in a directionperpendicular relative to the adapter axis A101′ is offset from thefirst reference plane P101′ in a direction toward the first or secondconnector port. The offset distance D220 is greater than what may beexpected based on normal manufacturing tolerances in the art, such aswhen the off-set is unintentionally more than zero. In some embodimentsthe offset distance D220 is greater than 0.05 mm (50 μm) and up to 0.2mm (200 μm).

The controlled order of installation can be utilized, for example, in acassette or a panel having a backside and a front side, where aplurality of fibers 108 can be connected by pre-installing a first setof fibers on the “backside” of the cassette or panel without buckling.The fibers 108 in the first set can be installed so that the end 109 ofthe fiber 108 is centered in each adapter. A second set of fibers isthen connected to the front side of the cassette using connectors 300.Optionally, the alignment device 220 can be off-set such that thealignment device extends further on the side of the second set (thefront side of the cassette) than the first set (the backside).

In one aspect, a second set of fibers is connected to the first setusing connector plugs with a buckling controller, e.g., a bucklingspring 610, to control the direction of buckling of the fibers 108 inthe second set of fibers. The connector plugs may be labelled “first”and “second” to indicate order of installation, where the “second” setincludes a buckling spring 610. The “first” set may be constructed to beshorter, as the “first” set does not need to include space for bucklingand may be constructed without buckling springs, thus allowing forsmaller cassettes, adapters, and/or connectors to be provided.

In one aspect, the direction of buckling is controlled by providing afiber buckling controller that can be used with the ferrule-less fiberconnector, where the optical fiber is axially movable relative to theconnector tip. The fiber buckling controller includes a flex member thatcan elastically flex from a first flex position to a second flexposition, the first and second flex positions being axial positionsrelative to the fiber connector tip. The fiber buckling controller canbe constructed so that the flex member moves between first and secondaxial positions when the connector body moves inside the adapter betweenfirst and second axial positions along an axis that extends through thefiber buckling zone. The flex member has a curving portion (e.g., aspring member 615) that in the second flex position has a sharpercurvature than in the first flex position. In one example, the curvingportion is straight or only has a slight curve when the flex member isin the first flex position. The flex member is configured to positivelyforce the optical fiber to buckle within the buckling zone as the flexmember moves from the first flex position to the second flex position.

The fiber optic adapter can be constructed to include a positive stopthat stops the movement of the connector tip when the connector tipengages the positive stop. The fiber optic connector can continue tomove into the connector port, causing the connector body 322 to movefrom a first axial position to a second axial position. Continuedmovement of the connector body 322 can then cause the flex member tomove from the first flex position to a second flex position, thuscausing the buckling of the fiber 108 in the same direction (e.g.,upward) as the flex member. The connector body 322 will stop at an endpoint (e.g., second axial position), where the flex member reaches thesecond flex position.

One example of the flex member is a buckling spring 610 shown in FIGS.16A, 16B, and 17A-17D. The buckling spring 610 can be disposed insidethe connector plug body 322′ in front of the lead-in section into thealignment device 220 as shown. The buckling spring 610 has a heightH610, width, and length L610 (as measured in a non-tensioned position),and a spring member 615 extending between a first end 611 and a secondend 612. The connector plug body may be provided with a channel 625 forhousing the fiber 108 and the buckling spring 610. The channel 625 has alength extending axially from a first end to a second end of the channel625, a height perpendicular to the length, and a width extendinglaterally perpendicular to the length and the height. The length andheight control the maximum extent of buckling that the buckling spring610 and the fiber can experience in the channel 625. In some examplesthe length is about 3-8 times as long as, about 4 times as long, orabout 8 times as long the height. The width of the channel 625 isconstructed to accommodate the width of the buckling spring and tominimize buckling in the lateral direction. For example, the width canbe about the width of the optical fiber, or from about 0.125 mm (125 μm)to 2 mm, or from about 0.125 mm to about 0.5 mm (500 μm). The width ofthe buckling spring 610 can be just slightly less than the width of thechannel 625 so that the buckling spring 610 fits in the channel 625 andcan move when the ends of the buckling spring 610 are brought closertogether by the insertion of the plug into the adapter. The connectorplug body may be provided with an insert 630 that defines the channel625.

FIGS. 17A-17D show sequential diagrammatic views of the connector plugbody 322 being introduced into a fiber optic adapter 100. The bucklingspring 610 has a length L610 at rest, and as the connector plug body 322is pushed further into the adapter 100, the buckling spring 610 iscompressed and the length of the buckling spring 610 becomes shorter(shown as L0, L1, L2, and L3). The buckling spring 610 directs thebuckling of the fiber 108. The buckling spring 610 continues to bow andto push the fiber 108 in a pre-determined direction (upward in thefigures) until the connector plug body 322 is fully seated in theadapter 100.

The buckling spring 610 can be constructed out of any suitable material.In one implementation, the buckling spring 610 is constructed from hightemperature thermoplastic that retains its plasticity even afterexposure to elevated temperatures. In preferred embodiments, thebuckling spring 610 remains flexible throughout the useful lifetime ofthe connector plug, and provides flexibility to the fiber in the eventthat the connector plug is unplugged or put under tension from the rear.The flexible buckling spring 610 can maintain the fiber mating locationnear the center of the alignment mechanism even when the connector plugis tensioned.

Biased Alignment

The fiber insertion axis I is generally aligned with the fiber alignmentslot 260, 460. However, when the fiber is inserted into the fiberalignment slot 260, 460 and the fiber biasing members (e.g., first,second, third (or further) balls 270, 271, 272) are inserted to push thefiber into the fiber alignment groove 105, the fiber biasing members maybe balanced atop the fiber 108 and may fall onto one side or the other,causing the biasing force to be off-center, potentially misaligning thefiber. When the off-centered alignment is uncontrolled, it may result inoptical losses and cause undesirable variability in the fiberconnection. In order to control the direction of the biasing force, thefiber biasing members (e.g., first, second, third (or further) balls270, 271, 272) can be intentionally biased in a controlled manner towardone side in a lateral direction. The fiber contact members can be biasedeither by constructing the elongated access slot 234 to be off-set fromthe fiber alignment groove 105, or by directing the biasing force towardone side using the biasing arrangement. In one example, the fiberalignment groove 105 is bisected by a reference plane P that includesthe axis of the adapter axis and the insertion axis I, and the fiberbiasing members are offset in a lateral direction from the referenceplane P by a lateral distance D260. The offset distance is greater thanwhat may be expected based on normal manufacturing tolerances in theart, such as when the off-set is unintentionally more than zero.Generally, the offset distance is less than the thickness of the fiber.In some embodiments the lateral distance (offset) D260 is at least 0.05mm (50 μm) and up to about 0.125 mm (125 μm).

An exemplary implementation of an off-set fiber contact member (fibercontact rod 273) is shown in FIG. 18 . The depicted embodiment includesa fiber contact rod 273 that biases the fiber into the fiber alignmentgroove 105. The elongated access slot 234′ for the fiber contact rod 273is positioned off-center by distance D260 as compared to the fiberinsertion axis I. The alignment structure can also be constructed withballs or other fiber biasing members.

Lead-In Funnel

The adapter body 101′ comprises a lead-in section 160 with a funnelportion 162 and a cylindrical portion 164. According to one aspect shownin FIG. 19 , the cylindrical portion 164 has tapered walls 165. Thecylindrical portion 164 includes a first width W31 at the proximal endand a second width W32 at the distal end, where the distal end is theplug end that is plugged into the adapter and disposed adjacent to thealignment device 220. In an embodiment, the tapered walls 165 widentoward the distal end such that the second width W32 is greater than thefirst width W31. Thus, when the fiber is inserted into the lead-insection 160, it less likely to come into contact with the tapered walls165 or any dust or dirt that may have been collected there. The secondwidth W32 can be greater than the first width W31 by at least twice thewidth of the optical fiber. For example, the second width W32 can begreater than the first width W31 by at least 0.25 mm (250 μm). In oneembodiment, the second width W32 is greater than the first width W31 byabout 0.25 mm to about 0.5 mm.

To provide the lead-in section 160 with the tapered walls 165, theadapter body 101′ may be constructed out to two halves 101A, 101B, asshown in FIG. 19 .

Example 1

Exemplary alignment devices were prepared according to the embodimentshown in FIGS. 8A-8E for testing optical loss. The alignment devicesincluded three balls that were biased against the fibers using threesprings. The overlap of the fiber tips (i.e., the excess length of thefree fiber tips when two fiber connectors are connected) was arranged at20 μm, 120 μm, 360 μm, and 600 μm. The optical loss across the fiberconnection was measured and recorded. The results are shown in FIGS.20A-20D. It was observed that the optical loss was significantly lowerthan in the testing using two balls, and was not as dependent on theamount of overlap or the position of the mating interface within the±400 μm window of measurement.

Various modifications and alterations of this disclosure will becomeapparent to those skilled in the art without departing from the scopeand spirit of this disclosure, and it should be understood that thescope of this disclosure is not to be unduly limited to the illustrativeexamples set forth herein.

What is claimed is:
 1. A fiber optic connector comprising: a plug bodydefining a distal plug end and an opposite proximal end; an opticalfiber defining a fiber axis, the optical fiber extending along the fiberaxis at least partially through the plug body, the optical fiberincluding a free end portion that extends outwardly from the plug bodydistally beyond the distal plug end, the free end portion of the opticalfiber not being supported by a ferrule; a shutter pivotally connected tothe plug body, the shutter being pivotally movable relative to the plugbody between an open position and a closed position, the shutterincluding an inside wall with a planar center portion having an interiorreceptacle that contains gel used to protect and clean the free endportion of the optical fiber when the shutter is in the closed position,wherein the interior receptacle receives the free end portion of theoptical fiber and causes the free end portion of the optical fiber tobend away from the fiber axis when the shutter is in the closedposition; and a reflective structure integrated with the inside wall ofthe shutter that reflects light away from the optical fiber.
 2. Thefiber optic connector of claim 1, wherein the reflective structureincludes a plurality of angled facets.
 3. The fiber optic connector ofclaim 1, wherein the reflective structure includes a guiding portion anda tip-receiving portion that are part of an integrated depression in theplanar center portion of the shutter.
 4. The fiber optic connector ofclaim 1, wherein the reflective structure is formed as a cut-out orgroove on the planar center portion of the inside wall of the shutter.5. The fiber optic connector of claim 3, wherein the reflectivestructure has a back wall and sloping side walls that lead into thetip-receiving portion.
 6. The fiber optic connector of claim 5, whereinthe back wall of the reflective structure includes one or more angledfacets that reflect light away from the optical fiber.
 7. The fiberoptic connector of claim 3, wherein the tip-receiving portion has sidewalls that partially circumscribe the free end portion of the opticalfiber.
 8. The fiber optic connector of claim 3, wherein the guidingportion of the reflective structure terminates in a corner where thefree end portion of the optical fiber is received.
 9. The fiber opticconnector of claim 3, wherein the tip-receiving portion includes agroove that extends from the guiding portion of the reflective structureto an opposite edge of the planar center portion of the shutter.
 10. Thefiber optic connector of claim 9, wherein the groove includes a singleangled facet for directing light from the optical fiber.
 11. The fiberoptic connector of claim 1, wherein the reflective structure includes asingle groove with faceted side walls and top and bottom walls.
 12. Thefiber optic connector of claim 11, wherein the single groove extendsfrom one edge of the planar center portion of the shutter at leastpartially to an opposite edge of the planar center portion.
 13. Thefiber optic connector of claim 1, wherein the reflective structureguides the free end portion of the optical fiber toward a facetedsurface at a specific angle.
 14. The fiber optic connector of claim 5,wherein the free end portion of the optical fiber is bent by thetip-receiving portion of the reflective structure, and wherein a shallowangle of the back wall diverts light coming from the optical fiber. 15.The fiber optic connector of claim 2, wherein the plurality of angledfacets are disposed at an angle of 5 degrees to 45 degrees relative to aplane perpendicular to the fiber axis.
 16. The fiber optic connector ofclaim 2, wherein the plurality of angled facets are disposed at an angleof 8 degrees to 30 degrees relative to a plane perpendicular to thefiber axis.
 17. The fiber optic connector of claim 2, wherein theplurality of angled facets are disposed at an angle of 10 degrees to 0degrees relative to a plane perpendicular to the fiber axis.
 18. Thefiber optic connector of claim 2, wherein the plurality of angled facetsare disposed at an angle of 12 degrees to 16 degrees relative to a planeperpendicular to the fiber axis.
 19. The fiber optic connector of claim3, wherein the tip-receiving portion is positioned at a distance from acenter of the planar center portion, and wherein the tip-receivingportion is positioned 10 percent to 90 percent of the way from thecenter toward an edge of the planar center portion.
 20. A fiber opticconnector comprising: a plug body defining a distal plug end and anopposite proximal end; an optical fiber defining a fiber axis, theoptical fiber extending along the fiber axis at least partially throughthe plug body, the optical fiber including a free end portion adjacentto the distal plug end, the free end portion of the optical fiber notbeing supported by a ferrule; a shutter pivotally connected to the plugbody, the shutter being pivotally movable relative to the plug bodybetween an open position and a closed position, the shutter having aninterior receptacle that contains gel used to protect and clean the freeend portion of the optical fiber when the shutter is in the closedposition; and a reflective structure integrated with the shutter withinthe interior receptacle configured to reflect light away from theoptical fiber.
 21. A fiber optic connector comprising: a plug bodydefining a distal plug end and an opposite proximal end; an opticalfiber defining a fiber axis, the optical fiber extending along the fiberaxis at least partially through the plug body, the optical fiberincluding an end portion positioned adjacent the distal plug end; ashutter being movable relative to the plug body between an open positionand a closed position, the shutter having an interior receptacleincluding a light distribution structure and a gel, wherein the endportion of the optical fiber contacts the gel when the shutter is in theclosed position.
 22. The fiber optic connector of claim 21, wherein theshutter being movable relative to the plug body comprises the shutterbeing pivotally movable relative to the plug body.
 23. The fiber opticconnector of claim 21, wherein the end portion is a bare fiber end.